ineffective

Ineffective is an adjective used to describe something that fails to produce the intended result or desired effect. The term is formed from the negative prefix in- attached to effective, which itself derives from Latin efficere "to bring about" and effect. In common usage, an ineffective action, method, or instrument does not achieve its stated goals.

In medicine, an ineffective treatment or intervention fails to relieve symptoms, halt disease progression, or improve health outcomes compared with a standard of care or placebo. In policy or organizational contexts, an ineffective program or strategy does not produce the intended benefits, such as cost savings, improved performance, or social impact. In communication and education, ineffective messaging or instruction fails to inform, persuade, or teach as intended.

Assessment of effectiveness relies on predefined criteria and evidence. Outcomes may be measured in terms of statistical significance, practical significance, or user satisfaction. An intervention can be labeled ineffective because of design flaws, incorrect implementation, inappropriate context, or insufficient duration. Conversely, a result may appear ineffective in the short term but prove beneficial later, or under different conditions.

An important distinction is between ineffective and inefficient: ineffective refers to lack of impact, while inefficient refers to poorer use of resources to achieve impact. A determination of ineffectiveness should consider study quality, biases, and consistency of results across settings.

Notes: the term is evaluative and context-dependent; declaring something ineffective does not necessarily imply it may not be improved or repurposed.